Science File

Caterpillar Species Spins Webs to Prey on Snails

Biologists have discovered a new species of caterpillar in the Hawaiian rain forest that ensnares snails in silken webs, then feasts on them until nothing but the shell is left.

It's the first time such behavior has been documented in caterpillars -- or any member of its biological order, Lepidoptera, which includes moths and butterflies.

"It was like finding a wolf that dives for clams," said University of Hawaii biologist and entomologist Daniel Rubinoff, who reported the discovery with William P. Haines, a biologist at the university, in Friday's edition of the journal Science.

Though all caterpillars have silk glands, this species is the first to be seen using theirs like a spider does. And though nearly all lepidopterans are vegetarians, "this caterpillar wouldn't sample foliage even if it were starving," Rubinoff said.

Rubinoff said the new species, Hyposmocoma molluscivora, would not have been able to develop such a novel feeding strategy without the isolation of the Hawaiian archipelago.

Such isolation, as Charles Darwin noted in his 19th century study of the Galapagos archipelago, favors the evolution of unique species, giving them millions of years of relaxed ecological competition in which to develop new ways of milking the most out of their environment.

With the destruction of much of the caterpillar's habitat, that isolation may have ended, Rubinoff said. But part of the habitat is protected, giving researchers "the chance to decipher more of their mysteries," he said. "We may find yet other novel, uniquely Hawaiian species."